Polyacrylamide (PAM) and hydrolyzed polyacrylamide (HPAM) are common water soluble polymers that have found application in oil field chemicals, paints, paper making, cosmetics, etc. The solution rheology of these materials define their use in these applications. With these polymers, aqueous viscosification or thickening is achieved through a combination of high molecular weight and chain expansion due to repulsion of pendent ionic groups along the polymer chain. High molecular weight polymers are difficult to prepare and dissolve and are also sensitive to shear. Viscosification due to charge repulsion is salt sensitive and thus, finds limited utility in highly saline systems.
Polymerizable esters of acrylic acid or methacrylic acid with alkyl or alkylaryl poly(ethyleneoxy)ethyl alcohols are disclosed in Dickstein U.S. Pat. No. 4,075,411; Trecker, U.S. Pat. No. 3,896,161; and British Pat. No. 828,496. Such monomers have found use in the preparation of stable latexes and special textiles. ##STR2##
Copolymers of base-neutralized acrylic acid and nonionic surfactant acrylates have also found use as thickeners for both aqueous solutions and water/organic liquid emulsions (Koenig and Bryant, U.S. Pat. No. 4,268,641). Improved NaCl tolerance is also taught therein. A liquid composition useful as a thickening agent in polymer latexes, comprising a mixture of solvent and a terpolymer of acrylic acid, an ester of the formula of: ##STR3## and an alkyl acrylate or methacrylate is claimed in U.S. Pat. No. 4,138,381.
In U.S. Ser. No. 454,286, now U.S. Pat. No. 4,463,152, Schulz, Maurer, and Bock (Exxon) disclosed copolymers having the formula which comprise: ##STR4## wherein R.sub.1 is selected from the group consisting of C.sub.1 to C.sub.20 alkyl groups, C.sub.6 to C.sub.20 aryl groups and C.sub.6 to C.sub.30 alkylaryl groups; R.sub.2 is hydrogen or a methyl group, n is about 1 to 60; y is about 0.010 to about 5.00 mole %, and x is about 95.00 to about 99.99 mole %.
U.S. Pat. No. 4,268,641 teaches base-neutralized copolymer having copolymerized therein about 90-99 mole percent of a carboxylic acid containing unsaturated hydrocarbon and about 1-10 mole percent of a nonionic surfactant acrylate having the formula: EQU R.sub.1 --(A).sub.x --OC(O)--CR.dbd.CH.sub.2
wherein R is H or CH.sub.3, R.sup.1 is a hydrophobe selected from the group consisting of alkyl--O--, alkyl--CH--, and alkyl--CO--, where alkyl contains 4-30 carbon atoms, A is a divalent radical selected from the group consisting of oxyethylene or oxyalkylene units or mixed oxyalkylene units --(OC.sub.n H.sub.2n).sub.x where n is an integer from 2 to 4 and x is an integer of 5-40, said surfactant acrylate having an HLB (hydrophilic lipophilic balance) value of about 10-19. Improved NaCl tolerant thickening is also taught. However, the polymers displaying the optimum NaCl compatibility were those with very high acrylic acid contents (98-99 mole%). Moreover, the preferred method for preparing these copolymers is by heterogeneous precipitation polymerization from organic solvents (nonsolvents for the polymer) like benzene, toluene, xylene, tetralin, etc. Precipitation polymerizations often have non-uniform copolymer composition because the product tends to precipitate before reaching complete conversion or ultimate chain length.
U.S. Pat. No. 4,421,902 discloses copolymers which are derived from at least 10 wt.% of an unsaturated acid monomer, 0.5-25 wt.% of an alkyl polyoxyethylene poly-(carbonyloxyethylene) acrylate (I), 0-0.1 wt.% of a polyethylenically unsaturated monomer and optionally an unsaturated comonomer (II). The acid monomer is methacrylic, acrylic, itaconic, acryloxypropionic, maleic, fumaric, itaconic or crotonic acid. (I) has the formula H.sub.2 C.dbd.CH--C(O)--O--(CH.sub.2 CH.sub.2 C(O)--O)x--(CH.sub.2 CH.sub.2 O)nR, where R is 8-30C alkyl, alkyaryl or polycyclic alkyl, x=0.1-10 and n is at least two and is up to 60 on average. Up to 50% of the (CH.sub.2 CH.sub.2) units can be substituted by 1,2-oxypropylene or oxybutylene units. (II) has the formula CH.sub.2 .dbd.CYZ where Y is H with Z as COOR', C.sub.6 H.sub.4 Z,CN, Cl, CONH.sub.2, OC(O)Z' or CH.dbd.CH.sub.2 ; Y is 1-4C alkyl with Z as COOR', C.sub.6 H.sub.4 Z, CN, CONH.sub.2 or CH.dbd.CH.sub.2 ; R' is 1-8C alkyl or 2-8C hydroxyalkyl or alkoxy (2-8C alkyl); Z is H, Cl, Br or 1-4C alkyl; Z is 1-8C alkyl; or Y and Z can both be Cl. Good salt tolerance is also taught but not exemplified therein. Also, such polymers include ##STR5## groups in the backbone which are known to be weak hydrolyzable links. In addition, products of this invention are aqueous dispersions of water-insoluble emulsion copolymers which require base neutralization for solubilization.
The present invention relates to terpolymers of acrylamide, acrylic acid (salt), and nonionic polyether surfactant acrylates of the formula ##STR6## wherein R.sub.1 is selected from a group consisting of C.sub.1 -C.sub.20 alkyl groups, C.sub.6 to C.sub.20 aryl groups, or C.sub.6 to C.sub.30 alkylaryl groups; R.sub.2 is hydrogen or a methyl group, n=1 to 60; x is 65-98 mole%; y is 2-35 mole%; z is 0.1 to 3.0 mole%.